How to create URL in ASP.Net MVC

by Andy
Posted on November 10, 2014July 29, 2020

This is probably a little old, but I am having some trouble so I figured I would start a post to see if I could help some people and possibly get some help myself. I have a Controller that is handling a shopping cart. The index method is pretty straight forward. Two parameters: the Cart it self and a returnURL as a string.

public ViewResult Index(Cart cart, string returnUrl = null)
        {
            CartIndexViewModel model = new CartIndexViewModel();

            model.Cart = cart;
            model.Cart.CartTotal = cart.ComputeTotalValue();

            model.Cart.QtyTotal = cart.CalculateTotalQty();
            model.ReturnUrl = String.IsNullOrWhiteSpace(returnUrl) ? Url.Action(&quot;Index&quot;, &quot;Home&quot;) : returnUrl;

            return View(model);
        }

public ViewResult Index(Cart cart, string returnUrl = null)

{

CartIndexViewModel model = new CartIndexViewModel();

model.Cart = cart;

model.Cart.CartTotal = cart.ComputeTotalValue();

model.Cart.QtyTotal = cart.CalculateTotalQty();

model.ReturnUrl = String.IsNullOrWhiteSpace(returnUrl) ? Url.Action("Index", "Home") : returnUrl;

return View(model);

}

The returnURL if it is empty should have a “default” URL that it can use. (This is where the trouble came in.) In trying to be a good developer I added a test method to test this particular piece of code.

 [TestMethod]
        public void Cart_Index_Test()
        {
            Item i1 = new Item() { ID = 1, Title = "Test", Price = 12.95M };
            Item i2 = new Item() { ID = 2, Title = "Test2", Price = 13.99M };

            Cart cart = new Cart();

            cart.AddItem(i1, 1);
            cart.AddItem(i2, 1);

            CartController target = new CartController();

            ViewResult result = target.Index(cart);

            Assert.IsInstanceOfType(result, typeof(ViewResult));

        }

[TestMethod]

public void Cart_Index_Test()

{

Item i1 = new Item() { ID = 1, Title = "Test", Price = 12.95M };

Item i2 = new Item() { ID = 2, Title = "Test2", Price = 13.99M };

Cart cart = new Cart();

cart.AddItem(i1, 1);

cart.AddItem(i2, 1);

CartController target = new CartController();

ViewResult result = target.Index(cart);

Assert.IsInstanceOfType(result, typeof(ViewResult));

}

This is where the issue comes in. This test continually fails with a NullReferenceException. I originally thought it was that the returnUrl value was null. Which lead me to post a question on StackOverflow. (I will save that rant for another post.) Then as I was stepping through the debugger for the unit testing I discovered that the problem is not the returnURL being null, it is that the this.URL.Action object is actually null. (Which would not happen in a normal “live” or even a debugging environment. It is because I was running the test on that controller that caused the issue.

This brings me to the issue, how would one create a URL in an MVC controller as to avoid the NullReferenceException in the test, and still have the code work properly in production?